Angraecum elephantium seedling in trouble!
 

I got this seedling in flask as a freebie at a show last October. Since then it's never given me reason to worry: grown a massive new root and a leaf to match the ones it had in flask. It had just started a new leaf. It has a bulge I think is probably a new root starting. Last night I noticed the new leaf has rotted. Looks fine otherwise: just the new leaf has collapsed into dark green wet tissue paper.

I can't really see (and sorry the picture isn't great), but I think there's a chance the leaf was broken. It did get knocked over recently. It also got watered more than it usually does so I'm hoping it's not that it got too wet... The discoloration on the root is just surface and has been there for months.

Anyone had anything happen like this before? If that leaf is rotted to the base is there a chance it will survive? Do they get crown rot? This is my first/only Angraecum and it was doing so well this is a bit of a shock!

Some angraecoid orchids really do not appreciate extra water - I killed a Sobennikoffia with too much water.
They're pretty much monopodial, so yes, they can suffer from crown rot, fatally. :( There is a chance the terminal bud is still OK - don't toss it out until the entire thing is brown and dead, it may sprout another shoot elsewhere on the plant.

Ak. I've basically only been spraying the little bit of moss it's in up till now. But it's recently been moved out of where it was to make way for new flasklings and it got watered with the big plants... Soon as I did it I thought it was a lot wetter than it had been... It's dried out a bit now, so fingers crossed I guess. If it gets through this I think I'll be moving it into chunky bark!

If the rot didn't go down too far, pour isopropyl alcohol in the middle to disinfect and prevent the destruction of the crown. If the crown isn't infected, a new leaf will appear in due time. I have been fortunate enough to save a few orchids this way. They also can, like phals, grow new plants from the side. My elephantinum is mounted and hung so that it gets good airflow. I also have found that mine do better with a bit of extra calcium. Hope yours will be fine! Good luck!

Pouring hydrogen peroxide on/into the crown is probably the best/most gentle way to stop crown rot (for young seedlings) from what I've heard... I hope it isn't crown rot, and it keeps on growing for you!

If you use hydrogen peroxide, make certain it is fresh. It slowly turns to water and oxygen. :)

Thanks for the tips. Tipping something in sounded a good idea, but I've decided not to. The dead leaf disapears out of sight but is looking as if it's drying out, so I'm sort of thinking at this stage it's either already gone too far or stopped itself, and it would be a gamble introducing more liquid down in there. Definitely sounds a good thing to try in many cases. Hope I've made the right call this time!

There is a bit of a dark spot on the bulge. Really hoping it's just a root pushing through and not linked to this: if there's rot between the top and that point then I don't think it's hopeful.

It is perfectly safe to use isopropyl alcohol. It is used in many aspects for its reliable ability to dry and disinfect. The angraecum encyclopedia is no longer on the web, unfortunately, or I would recommend you there. Angraecums do need good airflow though not necessarily a fan. Just hang it or see that it has some airspace. Elephantinum needs a little more light than didieri (they are often mistaken for each other). It is one that tolerates cooler winter temps (10'C). I give all but my distichum cattleya light. Good luck!

I don't have any in at the moment. I might get some if I'm passing a chemists. I think it's known as sugical spirit here? Not sure...

Sounds likely. It is often used before shots and IV's and that sort of thing. :)